FTC Bureau of Consumer Protection Director Jessica Rich said in a letter to the two companies:

We want to make clear that, regardless of the acquisition, WhatsApp must continue to honor these promises to consumers. Further, if the acquisition is completed and WhatsApp fails to honor these promises, both companies could be in violation of Section 5 of the Federal Trade Commission Act and, potentially, the FTC’s order against Facebook.

Rich’s letter to Facebook and WhatsApp stressed that any changes to how the messaging application handles user data must be approved by its user base, and users must be given the opportunity to opt out of future changes along those lines.

The CDD responded to Thursday’s announcement with the following statement:

We believe that despite claims that Facebook would preserve WhatsApp’s more privacy-friendly approach, the ultimate plan was to expand its mobile data-collection practices and fully integrate it into Facebook. Facebook’s future depends on its ability to successfully grow its mobile advertising, commerce, and payment applications. It did not spend $ 19 billion without planning to reap huge financial rewards by turning WhatsApp into an effective monetization machine for Facebook. The FTC is to be commended for sending a very strong signal that it will hold Facebook and WhatsApp accountable for their promises. The commission’s action has likely spoiled, for now, the plans Facebook has developed to turn its $ 19 billion shopping spree into even more digital gold for itself.